The subject matter described herein relates generally to electric power device testing and, more particularly, to methods and apparatus for testing full-power converter assemblies.
At least some known full-power converter assemblies, or power converters, are electrically tested up to their predetermined electrical ratings prior to shipping from a manufacturing facility to an installation site. One such test is typically referred to as a “full-power test”. Such full-power testing verifies performance of each power converter at their rated capacities. Smaller power converters, i.e., those power converters rated for 500 kilowatts (kW) or less are typically tested with testing apparatus that includes a full-power transformer, a full-power circuit breaker, and appropriately sized variable test loads that include motors with an adjustable brake and/or variable load resistor banks. However, for larger power converters in excess of 500 kW, the size and costs of the testing apparatus increases commensurately. Further, for those power converters with full-power ratings in excess of 2 megawatts (MW), including those power converters with power ratings in excess of 10 MW, the larger testing apparatus is expensive to purchase, install, and maintain, requires a large physical footprint, and may be unwieldy to position for testing power converters of varying sizes.
Also, at least some known power converter testing apparatus is typically electrically coupled to a local utility grid to supply the necessary testing power. However, not all such utility grids are sufficiently powered to support large-scale power converter testing. For example, utility grid connections in remote areas may not have the necessary voltage stability and may not have the necessary sustained current supply capabilities. Moreover, bulk power purchasing from a utility on a transient basis may be expensive and may require coordination with the associated utility such that the utility can be prepared to support the large transient electrical loads that full-power converter testing will likely entail.
Further, many known power converter testing apparatus include a “point of common coupling” that transmits electric power into the testing apparatus and receives at least some of the output power from the testing apparatus. Some testing procedures typically include testing power converters at electrical frequencies that may not be consistent with local grid frequencies. For example, a power converter designed for a 50 Hertz (Hz) frequency, as is common in Europe, is difficult to test with a 60 Hz North American grid. Grid operating requirements typically restrict harmonic frequencies transmitted thereon. Therefore, grid isolation equipment that may include expensive filters may be required to support test activities of power converters.